Angry protesters climbed the walls of the U.S. Embassy in Cairo on Tuesday and hauled down its American flags, replacing them with black flags with Islamic emblems.

The incident prompted U.S. security guards to fire off a volley of warning shots as a large crowd gathered outside, apparently upset about the production of a Dutch film thought to insult the Prophet Mohammed, said CNN producer Mohammed Fahmy, who was on the scene.

An embassy operator told CNN that the facility had been cleared of diplomatic personnel earlier Tuesday, ahead of the apparent threat, while Egyptian riot police were called to help secure the embassy walls.

Update: More pictures.

Update: Insanity rules the day. From the State Department’s Egyptian embassy website: